Systems and methods for characterizing an optical fiber performed in part by an optical node (12) in an optical line system (10) include performing one or more measurements to characterize the optical fiber (16, 18) with one or more components (50, 52) at the optical node (12), wherein the one or more components (50, 52) perform functions during operation of the optical node (12) and are reconfigured to perform the one or measurements independent of the functions; and configuring the optical node (12) for communication over the optical fiber (16, 18) based on the one or more measurements. The one or more components can include any of an Optical Service Channel (OSC), an Optical Time Domain Reflectometer (OTDR), and an optical amplifier. The configuring can include setting a launch power into the optical fiber based on the one or more measurements.

Aspects of the present disclosure describe amplifier dynamics compensation through feedback control for distributed fiber sensing systems, methods, and structures employing Brillouin optical time-domain reflectometry.

An objective is to provide an acoustic mode propagation speed measurement method and an acoustic mode propagation speed measurement device capable of measuring a propagation speed of an acoustic mode without cutting or processing an optical fiber wire.

According to the present invention, an acoustic mode propagation speed measurement method includes: acquiring a frequency shift spectrum of Brillouin scattered light generated in an optical fiber; fitting the frequency shift spectrum using a Gauss function; acquiring a spectral full-width at half maximum w from a fitted curve using the Gauss function; and calculating a propagation speed V.sub.A of an acoustic mode of the optical fiber by substituting the acquired spectral full-width at half maximum w into a linear function of the spectral full-width at half maximum w and the propagation speed V.sub.A of the acoustic mode.

An integrated fiber interferometry interrogator for generating superimposed waves is disclosed. The system is optimized for efficiency and vibration attenuation. The system comprises an optical light source for generating a first signal, a first signal splitter which splits the first signal into a reference signal and an interrogation signal, optical modulators for modulating the signals, a fiber coupler connected to a fiber under test, an isolator, a circulator with a plurality of connections for directing the signals, a signal mixer for mixing the signals into superimposed waves, and photo diodes for receiving the superimposed waves.

A method and system for determining deformation in a cable, where a sensing optical fiber arrangement is applied along the cable. The method includes injecting a forward pulse pump signal in the optical fiber in a forward direction of the optical fiber and injecting a reverse probe signal in the optical fiber in a reverse direction of the optical fiber. A stimulated Brillouin backscattering is measured and, based on the Brillouin backscattering measurement, information is provided about a deformation of the cable. The forward pulse pump signal is provided as a sum of a stationary signal component and an interrogation pulse component, the stationary signal component has an energy below a Brillouin activation level and the interrogation pulse signal component has an energy which results in that the sum of the stationary signal component and the interrogation pulse signal component exceeds the Brillouin activation level.

An optical fiber characteristics measuring apparatus includes: a light source that outputs frequency-modulated continuous wave of light; a first optical branching unit that branches the continuous light into pump light and reference light; a second optical branching unit that outputs backscattered light generated by making the pump light incident from one end of an optical fiber to be measured, wherein the backscattered light is Brillouin scattering in the optical fiber; a detector that detects interference light of the backscattered light and the reference light; a measuring unit that measures characteristics of the optical fiber by using a detection signal output from the detector; and a controller that controls the light source to change modulation frequency of the continuous light in units of one period or half a period of a modulation period corresponding to the modulation frequency.

The present invention is to provide a backscattered light amplification device, an optical pulse test apparatus, a backscattered light amplification method, and an optical pulse test method for amplifying a desired propagation mode of Rayleigh backscattered light with a desired gain by stimulated Raman scattering in a fiber under test having the plurality of propagation modes. The backscattered light amplification device according to the present invention is configured to control individually power, incident timing, and pulse width of a pump pulse for each propagation mode when the pump pulse is incident in a plurality of propagation modes after the probe pulse is input to the fiber under test in any propagation mode.

An optical pulse test apparatus according to the present disclosure includes a light generation unit configured to generate an optical pulse for generating backscattered light beams in an optical fiber under test and generate first light having an optical frequency for amplifying backscattered light in an LP11 mode out of the backscattered light beams in two LP modes through stimulated Brillouin scattering, and second light having an optical frequency for attenuating backscattered light in an LP01 mode out of the backscattered light beams in the two LP modes through stimulated Brillouin scattering, a mode demultiplexing unit configured to input the optical pulse, the first light, and the second light generated by the light generation unit into the optical fiber under test in the LP01 mode and separate, out of the backscattered light beams generated by the optical pulse, the backscattered light in the LP11 mode, a local oscillation light generation unit configured to generate local oscillation light by which the backscattered light separated by the mode demultiplexing unit is heterodyne-detected, a light reception unit configured to multiplex the backscattered light in the LP11 mode separated by the mode demultiplexing unit and the local oscillation light generated by the local oscillation light generation unit and photoelectrically convert the multiplexed light into an electrical signal, and an arithmetic processing unit configured to calculate a time-intensity distribution of the electrical signal obtained by the light reception unit photoelectrically converting the backscattered light in the LP11 mode.

The application discloses a light scattering parameter measurement system and its measurement method. Dual-frequency scattering interference technology is adopted to obtain distributed measurement of Rayleigh scattering parameters in an optical fiber. The Rayleigh scattering coefficient r and phase retardance θ are modulated on different components of the interference signal respectively by using the dual-frequency interference technology. The Rayleigh scattering coefficient r and phase retardance θ can be decoupled by simple filtering, to obtain separate measurements. A linear stretch is applied to the optical fiber under test, to add uniform phase change signals at all positions of the optical fiber under test. As a result, the term containing only Rayleigh scattering coefficient r can be extracted by low-pass filtering. The direct measurement of Rayleigh scattering parameters is of great significance to fundamental and application researches related to Rayleigh scattering of optical fiber.

An objective is to provide an acoustic mode propagation speed measurement method and an acoustic mode propagation speed measurement device capable of measuring a propagation speed of an acoustic mode without cutting or processing an optical fiber wire. According to the present invention, an acoustic mode propagation speed measurement method includes: acquiring a frequency shift spectrum of Brillouin scattered light generated in an optical fiber; fitting the frequency shift spectrum using a Gauss function; acquiring a spectral full-width at half maximum w from a fitted curve using the Gauss function; and calculating a propagation speed V.sub.A of an acoustic mode of the optical fiber by substituting the acquired spectral full-width at half maximum w into a linear function of the spectral full-width at half maximum w and the propagation speed V.sub.A of the acoustic mode.